Oropharyngeal excretion patterns of Epstein-Barr virus will be determined in various clinical conditions. Emphasis will be on the pharyngeal excretion of EB virus in patients with Burkitt lymphoma, in other African tumors and in control subjects. Oropharyngeal excretion of this virus in cases of infectious mononucleosis is being studied in relation to functional capacities of cell-mediated immunity during the course of disease. A major focus will be to establish which cells in the oropharynx of infectious mononucleosis cases are producers of small amounts of cell-free virus.